Toner compositions are used in electrophotographic and electrostatic printing processes (collectively electrographic processes) to form an electrostatic image on the surface of a photoreceptive element or dielectric element, respectively. These toner compositions comprise a binder element, a visual enhancement additive, and often a charge control additive or charge director. In conventional toner manufacture processing, a polymeric binder is formed and homogeneously mixed with the visual enhancement additive and any other components.
In certain product technologies, particles are provided with separate coatings. Such coated particles are known, for example, in the catalyst, pharmaceutical and cosmetic industries.
U.S. Pat. No. 6,037,019 discloses a process for adhering a powder to a substrate. The process includes the steps of: a) providing an oscillating magnetic field, b) continuously introducing into the magnetic field coating material, a substrate, and a means of affixing the coating material to the substrate by forming a fluidized bed of at least the coating material and providing sufficient force to cause the coating material to adhere to the surface of the substrate, and c) continuously collecting the coated substrate.
A process for adhering a liquid to a particulate substrate is disclosed in U.S. Pat. No. 5,962,082. The process comprises the steps of: a) providing an apparatus which can create an oscillating magnetic field within a chamber, b) providing particulate magnetic material within the chamber of said apparatus while said oscillating field is active, c) having in the chamber within the oscillating magnetic field a liquid coating material and a particulate substrate to be coated with said liquid, d) and having said magnetic field form a fluidized bed of at least said particulate magnetic material, said liquid coating material coating the surface of the particulate substrate, and e) optionally continuously collecting the coated particulate substrate.